Public trackers are usually sufficient for most requirements.
Other than that, keep an eye open on r/openinvites and other threads on reddit/forums.
Usually during bigger holidays (winter holidays, eastern, summer, black friday) they open the gates for newcomers.

Alternative: Usenet
Indexers like drunkenslug can, in a limited fashion, be used for free.

For anyone interested, here's the site operator's statement on the sudden closure:

https://rentry.co/h2ch4wfr

If you pinky promise to not be a bad person and can keep a decent ratio I can send you an invite to TorrentLeech. Just shoot me a message with an email to send the invite to.

I've been using digitalcore bc they were open when I joined, pretty good but idk if they're open rn